Technology of flat display has been significantly advanced recently, in part because manufacturing thin film transistors on a substrate such as glass has become a mature skill which facilitates the development of active matrix type display devices. In addition to liquid crystal materials which need a backlight when used for flat displays, an electro-luminescent device, such as an organic light emitting diode (OLED), which can emit light itself, is actively researched. Because of the feature of self-light-emitting, among many other advantages, the display comprising electro-luminescent devices is brighter than a backlight display.
However, the brightness of the electro-luminescent device may decay over the time of usage. Moreover, the electro-luminescent devices of different colors may have different rates of brightness decay. For example, the blue light electro-luminescent device decays faster than the other colors. As a result, the CIE standard observer curve value of the electro-luminescent display shifts, and the color presented on the electro-luminescent display shifts toward yellow. This effect is called “color shift” in the display because the brightness of red, green, and blue color are no longer as even as designed.